The invention relates to a capacitance diode having an epitaxial layer of a first conductivity type provided on a substrate, a first zone of the first conductivity type formed therein by diffusion, and a surface-adjoining second zone of the second conductivity type forming a p-n junction with the first zone.
When such capacitance diodes are used, as is usual, as a tuning capacitance in parallel oscillatory circuits, the resonance curve of the oscillatory circuit is distorted due to the nonlinear characteristic of the diode.
This effect is described in "Valvo Berichte", Vol. XVII, No. 2, pp. 97-107 (in particular pp. 99-101). From this article it appears that when the capacitance diode is driven, a deviation of the resonant frequency f of .DELTA.f/f occurs in the oscillatory circuit with the voltage .DELTA.U.
In a prior art capacitance diodes this frequency deviation assumes comparatively large and both positive and negative values, which is very undesirable.